The analysis of vibrational overtone spectra of larger organic molecules is a most important step towards the understanding of the dynamics of such molecules. We will observe overtone spectra of larger molecules (ten or more atoms) in the mid to near infrared region using a high resolution Fourier transform infrared (FTIR) spectrometer (Bruker IFS120HR). The use of a long slit supersonic jet apparatus in combination with multipass optics will provide the necessary simplification of the spectra at sufficient high sensitivity. Our experimenal results will help in the construction of a more advanced theoretical model for the description of highly excited vibrational states of larger molecules. We also plan to carry out laser/FTIR double resonance experiments on the same subject. Further we expect that the improved experimental set-up will be sensitive enough to allow the observation of van der Waals or clusters using FTIR absorption spectroscopy.